<template>
  <el-select
    :value="valueTitle"
    :clearable="clearable"
    @clear="clearHandle"
  >
    <el-option
      :value="valueTitle"
      :label="valueTitle"
    >
      <el-tree
        id="tree-option"
        ref="selectTree"
        class="scroll"
        :accordion="accordion"
        :data="options"
        :props="props"
        :node-key="props.value"
        :default-expanded-keys="defaultExpandedKey"
        @node-click="handleNodeClick"
      />
    </el-option>
  </el-select>
</template>
<script>
export default {
  name: 'TreeSelect',
  props: {
    /* 配置项 */
    props: {
      type: Object,
      default: () => {
        return {
          value: 'value', // ID字段名
          label: 'label', // 显示名称
          children: 'children' // 子级字段名
        }
      }
    },
    /* 选项列表数据(树形结构的对象数组) */
    options: {
      type: Array,
      default: () => { return [] }
    },
    /* 初始值 */
    value: {
      type: [Number, String],
      default: () => { return '' }
    },
    /* 可清空选项 */
    clearable: {
      type: Boolean,
      default: () => { return false }
    },
    /* 自动收起 */
    accordion: {
      type: Boolean,
      default: () => { return false }
    }
  },
  data() {
    return {
      valueId: this.value, // 初始值
      valueTitle: '',
      defaultExpandedKey: []
    }
  },
  watch: {
    value() {
      this.valueId = this.value
      this.initHandle()
    },
    options: {
      handler(newValue, oldValue) {
        this.valueId = this.value
        this.initHandle()
      },
      deep: true
    }
  },
  mounted() {
    this.initHandle()
  },
  methods: {
    // 初始化值
    initHandle() {
      if (this.valueId) {
        this.$nextTick(() => {
          const node = this.$refs.selectTree.getNode(this.valueId)
          if (node != null) {
            this.valueTitle = node.data[this.props.label] // 初始化显示
            this.$refs.selectTree.setCurrentKey(this.valueId) // 设置默认选中
            this.defaultExpandedKey = [this.valueId] // 设置默认展开
          }
        })
      } else {
        this.valueTitle = '' // 清除缓存显示
      }
      // this.initScroll();
    },
    // 切换选项
    handleNodeClick(node) {
      this.valueTitle = node[this.props.label]
      this.valueId = node[this.props.value]
      this.$emit('getValue', this.valueId)
      this.defaultExpandedKey = []
    },
    // 清除选中
    clearHandle() {
      this.valueTitle = ''
      this.valueId = null
      this.defaultExpandedKey = []
      this.clearSelected()
      this.$emit('getValue', null)
    },
    /* 清空选中样式 */
    clearSelected() {
      const allNode = document.querySelectorAll('#tree-option .el-tree-node')
      allNode.forEach((element) => element.classList.remove('is-current'))
    }
  }
}
</script>
<style lang="scss" scoped>
.el-scrollbar {
    .el-scrollbar__view {
        .el-select-dropdown__item {
            height: auto;
            max-height: 274px;
            padding: 0;
            overflow: hidden;
            overflow-y: auto;
        }
    }

}
</style>
